Abstract:

A tool made of powdered metal, such as a modified T15 HSS in powdered
form, and having a multi-lobular end profile for punching multi-lobular
recesses into workpieces, such as into the heads of fasteners. The tool
is homogenous and contains only carbides which are relatively small, such
as in the 1-4 micron range. Also provided is a method of fabricating such
a tool. The method requires that a powdered metal bar is cut and then the
cut piece is worked to provide the multi-lobular tool. The final part is
theoretically 100% dense, as opposed to being only 95-98% dense as in
metal injection molded parts. In use, the final part, due to how it is
fabricated, has increased column strength and increased impact
resistance.

Claims:

1. A method of fabricating a tool made of powdered metal, where the tool
has a multi-lobular end profile for punching multi-lobular recesses into
workpieces, said method comprising: providing a rod formed of powdered
metal; cutting a predetermined length from the rod, said predetermined
length defining a part; applying a chamfer to at least one end of the
part; grinding an outside diameter of the part to a predetermined size;
extruding a multi-lobular configuration on one end of the part; grinding
an outside diameter of the part to a predetermined size; and forming the
part to a predetermined length.

2. A method as recited in claim 1, further comprising stress relieving the
part in a heat treat furnace.

3. A method as recited in claim 1, further comprising coining a trademark
onto the part.

4. A method as recited in claim 1, further comprising facing the part to a
predetermined final length.

5. A method as recited in claim 1, further comprising shaving a nose angle
on the part.

6. A method as recited in claim 1, further comprising heat treating the
part to a predetermined hardness.

7. A method as recited in claim 5, further comprising polishing the nose
angle to desired finish.

8. A method as recited in claim 1, wherein the step of cutting a
predetermined length from the rod comprises cutting a predetermined
length from a rod formed of high speed steel.

9. A method as recited in claim 1, wherein the step of cutting a
predetermined length from the rod comprises cutting a predetermined
length from a rod formed of T15 high speed steel.

10. A method as recited in claim 1, wherein the step of cutting a
predetermined length from the rod comprises cutting a predetermined
length from a rod formed of high speed steel which includes molybdenum.

11. A method as recited in claim 1, wherein the step of cutting a
predetermined length from the rod comprises cutting a predetermined
length from a rod formed of T15 high speed steel which includes
molybdenum.

12. A method as recited in claim 1, wherein the step of applying a chamfer
to at least one end of the part comprises applying a
47.degree./45.degree. chamfer to both ends of the part.

13. A method as recited in claim 1, wherein the step of extruding a
multi-lobular configuration on one end of the part further comprises
applying oil to the part and extruding the multi-lobular configuration in
an extrusion die that is secured in a punch press.

Description:

RELATED APPLICATION (PRIORITY CLAIM)

[0001]This patent application is a divisional of U.S. patent application
Ser. No. 11/052,438, filed on Feb. 7, 2005, which claims the benefit of
U.S. Provisional Application Ser. No. 60/561,728, filed Apr. 13, 2004,
both of which are incorporated herein by reference in their entirety.

BACKGROUND

[0002]This invention generally relates to multi-lobular tooling for
punching a multi-lobular recess into, for example, the head of a
fastener. The invention more specifically relates to multi-lobular
tooling and tooling blank which are formed of powdered metal. The
invention also relates to methods of forming a powdered metal
multi-lobular tool.

[0003]Multi-lobular tools, often referred to as "punch pins," are used to
punch a multi-lobular recess into, for example, the head of a fastener.
FIG. 1 illustrates a multi-lobular punch pin 10. In use, the head 12 of
the punch pin 10, i.e., having a multi-lobular profile, is punched into a
workpiece, such as the head of a fastener, to form a multi-lobular
recess.

[0004]Typically, punch pins are formed of standard tool steel such as M42
tool steel. Tool steel, by nature, is very nonhomogeneous, and typically
contains large, often segregated carbides. FIG. 2 provides an image of a
punch pin formed of M42 tool steel, where the image was taken with a
microscope at 400×, along a transverse cross-section (i.e., along
line 2 in FIG. 1). FIG. 3 is similar, but is an image taken along a
longitudinal cross-section (i.e., along line 3 in FIG. 1). As shown,
carbides (the lighter areas in the image), many of which are relatively
large, can be found along either cross-section. With regard to size, in a
punch pin formed of conventional tool steel, carbides as large as 10-50
microns or even larger often exist.

[0005]The presence of a carbide segregation tends to produce a hard,
brittle or weakened plane, wherein the material has a tendency to
fracture or splinter. Generally speaking, it is undesirable for a punch
pin to contain large carbides and carbide segregation, as carbides
provide a point of weakness. This is especially true if a fairly large
carbide happens to exist along a lobe of a multi-lobular punch pin. In
such case, the carbide may cause the lobe to chip prematurely during use,
as shown in FIG. 4. FIG. 4 provides an image of a punch pin formed of M42
tool steel, where the image was taken with a scanning electron microscope
(SEM) at 35×, after the punch pin was used in a number of cycles to
punch multi-lobular recesses into workpieces. Not only does it present a
possible problem when a large carbide exists on a lobe of a punch pin,
but the problem is even more severe the larger the punch pin.

[0006]U.S. Pat. No. 6,537,487 discloses a method of molding a powdered
metal part using a metal injection molding ("MIM") process. Such a
process is relatively complicated and uses a binder. The binder must be
removed (i.e., de-binding) during sintering, or prior to sintering. A
finished part made with such a process typically is only 95 to 98% dense,
and has diminished column strength and limited impact resistance.

OBJECTS AND SUMMARY

[0007]An object of an embodiment of the present invention is provide a
multi-lobular tool and tool blank which are formed of powdered metal,
thereby providing that the tool is very homogenous and contains only
carbides of an extremely small nature.

[0008]Yet another object of an embodiment of the present invention is
provide a relatively simple method of fabricating a multi-lobular
powdered metal tool, where the method does not require any de-binding
steps, either prior to or during sintering.

[0009]Briefly, and in accordance with at least one of the foregoing
objects, an embodiment of the present invention provides a tool made of
powdered metal, such as a modified (in that molybdenum is added) T15 high
speed steel (HSS) in powdered form, and having a multi-lobular end
profile for punching multi-lobular recesses into workpieces, such as into
the heads of fasteners.

[0010]Another embodiment of the present invention provides a method of
fabricating a tool made of powdered metal, where the tool has a
multi-lobular end profile. The method includes steps of: cutting a
predetermined length from a rod formed of powdered metal, such as a
modified T15 HSS (modified in that molybdenum is added); applying a
47°/45° chamfer to both ends; grinding the outside diameter
to a predetermined size; applying oil and extruding a multi-lobular
configuration on one end of the cutoff in the extrusion die that is
secured in a punch press; stress relieving the part in a heat treat
furnace; coining a trademark (if desired) onto the part; grinding the
outside diameter to a predetermined size; facing to predetermined length;
shaving a nose angle; heat treating to a predetermined hardness; grinding
the nose angle to achieve a desired finish and length; grinding the
outside diameter step to a predetermined size and length; and polishing
the nose angle to desired finish.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]The organization and manner of the structure and operation of the
invention, together with further objects and advantages thereof, may best
be understood by reference to the following description, taken in
connection with the accompanying drawings, wherein like reference
numerals identify like elements in which:

[0012]FIG. 1 is a perspective view of a multi-lobular punch pin;

[0013]FIG. 2 provides an image of a punch pin formed of M42 tool steel,
where the image was taken with a microscope at 400×, along a
transverse cross-section (i.e., along line 2 in FIG. 1);

[0014]FIG. 3 is similar to FIG. 2, but where the image has been taken
along a longitudinal cross-section (i.e., along line 3 in FIG. 1);

[0015]FIG. 4 provides an image of a punch pin formed of M42 tool steel,
where the image was taken with a scanning electron microscope (SEM) at
35×, after the punch pin was used in a number of cycles to punch
multi-lobular recesses into workpieces;

[0016]FIG. 5 provides an image of a punch pin formed of a modified T15 HSS
in powdered form, in accordance with an embodiment of the present
invention, where the image was taken with a microscope at 400×,
along a transverse cross-section (i.e., along line 2 in FIG. 1);

[0017]FIG. 6 is similar to FIG. 5, but where the image has been taken
along a longitudinal cross-section (i.e., along line 3 in FIG. 1);

[0018]FIG. 7 provides an image of a punch pin formed of a modified T15 HSS
in powdered form, where the image was taken with a SEM at 50×,
after the punch pin was used in a number of cycles to punch multi-lobular
recesses into workpieces; and

[0019]FIG. 8 provides a flow chart of a method of fabricating a
multi-lobular tool, such as a punch pin, where the method is in
accordance with an embodiment of the present invention.

DESCRIPTION

[0020]While the present invention may be susceptible to embodiment in
different forms, there are shown in the drawings, and herein will be
described in detail, embodiments thereof with the understanding that the
present description is to be considered an exemplification of the
principles of the invention and is not intended to limit the invention to
that as illustrated and described herein.

[0021]As discussed above, FIGS. 2-4 relate to a punch pin formed of M42
tool steel. FIGS. 5-7 provide similar views, but relating to a
multi-lobular tool, specifically a punch pin, formed of a modified T15
HSS in powdered form (modified in that molybdenum is added), in
accordance with an embodiment of the present invention. As a result of
being formed of powdered metal, the punch pin is much more homogenous and
contains only carbides (the lighter areas in the images shown in FIGS. 5
and 6) which are relatively small, compared to carbides which are
typically contained in a punch pin formed of tool steel. As a result of
being more homogenous and containing only relatively small carbides, the
punch pin is very robust and not prone to chipping or otherwise failing
during use (i.e., while being used to, for example, punch recesses in the
heads of fasteners).

[0022]FIG. 5 provides an image of the punch pin, where the image was taken
with a microscope at 400×, along a transverse cross-section (i.e.,
along line 2 in FIG. 1). FIG. 6 is similar to FIG. 5, but where the image
has been taken along a longitudinal cross-section (i.e., along line 3 in
FIG. 1). As shown in FIGS. 5 and 6, the carbides (the lighter areas in
the images) are relatively small compared to those present in the tool
steel punch pin, as shown in FIGS. 2 and 3. Specifically, while the
carbides present in a punch pin made of tool steel can be 40 microns or
more, providing that the punch pin is formed of powdered metal, such a
modified T15 HSS in powdered form, provides that the carbides can be as
small as 1-4 microns.

[0023]FIG. 7 provides an image of the punch pin, where the image was taken
with a SEM at 50×, after the punch pin was used in a number of
cycles to punch multi-lobular recesses into workpieces. Comparing FIG. 7
to FIG. 4, the powdered metal punch pin (FIG. 7) exhibits merely
acceptable wear with no chipping, while the tool steel punch pin (FIG. 4)
exhibits some chipping at a lobe.

[0024]Because large carbides provide a point of weakness, and the lobes of
a multi-lobular tool, such as a punch pin, receive a lot of the stress
during impact, it is important to provide or insure that large carbides
do not exist at a lobe of a multi-lobular tool. Typically, multi-lobular
tools, such as punch pins, are formed of tool steel which is very
non-homogenous. Providing that the multi-lobular tool is instead made of
powdered metal, such as a modified T15 HSS in powdered form, provides
that the grain structure of the part is much more homogenous. As such,
there is less of a likelihood or even no likelihood, that large carbides
will exist in the area of, or on one of the lobes. As a result, the punch
pin is more robust and has improved column strength and impact
resistance, and will have a longer useful service life.

[0025]FIG. 8 illustrates a method of fabricating a powdered metal
multi-lobular tool, such as a punch pin as shown in FIGS. 5-7, where the
method is in accordance with an embodiment of the present invention. As
shown, the method provides the following steps: cutting a predetermined
length from a rod from bar stock formed of powdered metal, such as a
modified T15 HSS (modified in that molybdenum is added); applying a
47°/45° chamfer to both ends; grinding the outside diameter
to a predetermined size; applying oil and extruding a multi-lobular
configuration on one end of the cutoff in the extrusion die that is
secured in a punch press; stress relieving the part in a heat treat
furnace; coining a trademark (if desired) onto the part; grinding the
outside diameter to a predetermined size; facing to predetermined length;
shaving a nose angle; heat treating to a predetermined hardness; grinding
the nose angle to achieve a desired finish and length; grinding the
outside diameter step to a predetermined size and length; and polishing
the nose angle to desired finish. The process is relatively simple, and
does not require any de-binding steps, as opposed to a metal injection
molding process, where a binder must be removed during sintering, or
prior to sintering. A finished part made with such an injection metal
molding process typically is only 95 to 98% dense. In contrast, a
finished part fabricated with the above-described method is theoretically
100% dense, and has improved column strength, impact resistance, and tool
life.

[0026]To provide the powdered steel bar, before performing the fabricating
steps described above, the following process may be used:

[0027]1. Molten metal, of the proper composition, is atomized in an inert
atmosphere.

[0028]2. The resulting powered metal is sealed in a large steel "can"
which is a steel pipe 5 to 6 feet long and 10 to 12 inches in diameter.

[0029]3. The sealed can is placed in a hot isostatic press (HIP) which
exerts a pressure of 1000 atmospheres at a temperature 2100 F.

[0030]4. After the HIP process, the steel can is machined off of the now
solid and 100% dense P.M. ingot.

[0031]5. The P.M. ingot is then processed like a conventionally poured
ingot.

[0032]While embodiments of the present invention are shown and described,
it is envisioned that those skilled in the art may devise various
modifications of the present invention without departing from the spirit
and scope of the disclosure.